Cable distribution cabinets are used, for example, in telecommunications technology to connect a large number of domestic service connections to the underground cables.
For this purpose, the housing of the switchgear cabinet in which the distribution compartment with the clamping rails or further active electrical components is located, is positioned on a hollow pedestal, which extends at least partially into the ground and through which the underground cables are passed.
For reasons of protection against electric shock, the formation of condensation water etc., a bottom plate is arranged as a partition between the distribution compartment and the pedestal compartment, i.e. between the actual cabinet housing and the pedestal, and the underground cables extend upwards into the distribution compartment through said bottom plate.
A number of problem cases need to be taken into consideration here.
Firstly, when viewed in plan view, a fitting rack is usually fitted in the housing, and this fitting rack ensures the stability of the housing, and the individual components, in particular the blocks with the terminal strips, are screwed on the fitting rack.
When viewed in plan view, these blocks with terminal strips are located in the front region, approximately in the front half, of the basic outline of the housing. The underground cables should therefore pass through the bottom plate preferably in the rear region in order to be passed up from there behind the terminal strips to the required height.
Theoretically, the underground cables could also pass through the bottom plate in the front region, but in this case they would have to be bent back towards the rear below the lowermost terminal strip. As regards the thickness of the underground cables of usually more than 4 cm and the corresponding rigidity, this is in principle difficult, but is even more difficult, in view of the tight installation conditions, the further towards the bottom on the fitting rack the terminal strips begin because there is less space remaining for a deflection towards the rear between the cable passage in the bottom plate and the lowermost terminal rail.
Another problem is the damage to switchgear cabinets owing to motor vehicles being driven into them.
In this case, the outer protective paneling of the switchgear cabinet is often damaged, and this can be replaced relatively easily.
If, however, the frame and/or the bottom plate is also broken and needs to be replaced, the complexity involved is very great since the individual underground cables pass through this bottom plate through cable passages and therefore all of the underground cables need to be disconnected prior to the replacement and the switchgear cabinet needs to be lifted off from the pedestal before a new bottom plate can be fitted on the pedestal.
This also results in a long downtime of all of the domestic service connections suspended on this switchgear cabinet.
A further complicating factor is the fact that the housing usually comprises an inner frame, which is composed of profiles along the edges and onto which the outer paneling of the housing is applied, and this inner frame often reaches down beyond the boundary between the distribution compartment and the pedestal region and merely has horizontal transverse struts at the boundary, on which struts the bottom plate can be fastened.